Fuel flowing through a fuel injector typically exits at a nozzle end of the fuel injector. The nozzle end is believed to have a disk with at least one orifice to control, in part, the spray pattern and the direction of the fuel exiting the fuel injector.
The orifice is believed to be formed by drilling or by punching through a workpiece. The method of drilling orifices for fuel injector is believed to be electric discharge machining (EDM) that can form orifices of 150 to 200 microns in diameter. It is believed that one of the many disadvantages of EDM is the fact that the holes are typically formed without any favorable entry or exit geometry for the orifices, thereby affecting the flow through the orifices. It is believed that to maintain the same amount of fuel flow with the smaller orifice may require more than four times the number of the larger orifices. This is believed to reduce productivity in the manufacturing of the fuel injector. Additionally, it is believed that EDM forming of the orifices are not uniform between individual injectors, thereby causing the fuel injector spray to also be non-uniform between individual injectors.
Future emission standards for gasoline and diesel engines are believed to require the use of smaller orifices for smaller fuel spray droplets and shorter fuel spray duration. It is believed that fuel spray pattern and flow should remain uniform between adjacent cylinders in a multi-cylinder engine.
It is believed that smaller orifices can be formed with no loss in productivity through the use of laser machining. At least two techniques are believed to be used for laser machining orifices. One is trepanning or helical drilling, the other is percussion drilling. Percussion drilling is believed to be less than desirable due to the random nature of metal heating and expulsion that most likely results in a non-cylindrical or non-circular orifice. Trepanning, on the other hand, is believed to be more precise as a center hole is believed to be initially formed before the formation of the orifice. Helical drilling is similar to trepanning but without the initial formation of a center hole. However, it is believed that neither trepanning nor percussion drilling provides for a desired formation of entry and exit geometry in the orifices.
The present invention provides for at least one method of forming chamfers and an orifice together while maintaining dimensional consistency between a plurality of orifices formed by the method. In one preferred embodiment of the invention, the method is achieved by separating collimated light from at least one laser light source with a spatial filter; forming at least one orifice in a workpiece with the collimated light during a predetermined first time interval; and forming at least one chamfer with non-collimated light at a second time interval during the first time interval. The orifice formed by the method has an axis, which extends between a first surface and second surface of the workpiece with the at least one chamfer being disposed between the first surface and the second surface.
In another preferred embodiment, the method is also achieved by transmitting laser light in at least one predetermined mode; separating at least one of amplified spontaneous emission of light and non-collimated light from the at least one laser light source; forming at least one orifice in a workpiece with the laser light of the at least one predetermined mode during a predetermined first time interval; and forming at least one chamfer with at least one of the amplified spontaneous emission and non-collimated lights at a second time interval during the first time interval.
In a further embodiment of the invention, a laser system is provided to machine orifices and chamfers which are dimensionally consistent between respective orifices and chamfers. The laser system comprises at least one laser light source; at least one optical arrangement that directs collimated light towards a workpiece during a first time interval and non-collimated light towards the work piece during a second time interval that overlaps the first time interval. The optical arrangement includes focusing optic disposed between the at least one laser light source and the workpiece; at least one spatial filter disposed between the laser and the focusing optic; and at least one shutter and iris arrangement disposed between the spatial filter and the work piece.